The Defense Department has a half-dozen locations that feature subterranean networks. They're located at Fort Hood, Texas; Fort Story, Virginia; Fort Leonard Wood, Missouri; Camp Atterbury-Muscatatuck Urban Training Center, Indiana; Tunnel Warfare Center, China Lake, California and Yuma Proving Grounds, Arizona, according to the new subterranean training manual.
https://www.military.com/daily-news/2018/06/24/army-spending-half-billion-train-troops-fight-underground.html